KR20160040203A - Limited slip differential with separation of clutch and actuator - Google Patents

Abstract

The differential gear mechanism constructed in accordance with one example of the present disclosure may include a differential gear casing. The first and second side gears can be rotatably mounted in the differential gear casing. A pair of pinion gears can be mounted between the first side gear and the second side gear. Both pinion gears can be rotatably mounted on a cross shaft fixed to rotate with the differential gear casing. The clutch pack may include a plurality of annular plates sandwiched between a plurality of annular friction discs. The clutch pack may be provided on the first side of the cross shaft. The actuator assembly may include a piston received within the piston housing. The actuator assembly may be configured to actuate the clutch pack. The actuator assembly may be provided on a second side opposite the first side of the cross shaft.

Description

[0001] The present invention relates to a differential limiting device capable of separating a clutch and an actuator,

Cross reference of related application

This application is related to U.S. Patent Application No. 61 / 863,142 filed on August 7, 2013, U.S. Patent Application No. 61 / 864,119 filed on August 9, 2013, U.S. Patent Application No. 60 / 61 / 875,203, filed July 30, 2014, and U.S. Patent Application No. 62 / 030,683, filed July 30, The disclosures of the above applications are incorporated herein by reference.

The present disclosure relates generally to a differential gear assembly, and more particularly to a differential gear case arrangement in which a clutch and a piston actuator are configured at opposite ends of a differential gear case.

The differential gear mechanism is provided in an axle assembly and can be used to transfer torque from the drive shaft to a pair of output shafts. The drive shaft can drive the differential gear by using a bevel gear which meshes with the ring gear mounted on the housing of the differential gear. In the automotive field, differential gears rotate tires mounted at opposite ends of an axle assembly at different speeds. This is important because the outer tire moves along an arc of longer distance than the inner tire when the vehicle turns. Thus, the outer tire must rotate at a faster speed than the inner tire to compensate for a relatively longer travel distance. The differential gear includes a differential gear case and a gear device that can transmit torque from the drive shaft to the output shaft while rotating the output shaft at different speeds as needed. The gearing device may generally comprise a pair of side gears mounted to rotate with respective output shafts. A series of cross pins or pinion gear shafts are fixedly mounted to the differential gear case to rotate with the differential gear case. The corresponding plurality of pinion gears are mounted for rotation with the pinion gear shaft and are in engagement with the two side gears.

Some differential gear mechanisms include traction modifying differentials. Generally, the clutch pack can be disposed between one of the side gears and the adjacent surface of the differential gear case. A clutch pack or locking mechanism may be used to limit relative motion between the differential gear case and one side gear. In such a differential gear, coupling clutch packs or locking mechanisms (which slow differentiation) is accomplished by one of several different methods. Some configurations include a piston, which operates to move the clutch pack between an open state, a locked state and a partially locked state.

The description of the background art provided herein is intended to provide a general overview of the present disclosure. The background section describes not only the performance of currently designated inventors but also descriptions of aspects which may not be qualified as prior art at the time of filing the application or which are not expressly or implicitly recognized as prior art to this disclosure To some extent.

The differential gear mechanism constructed in accordance with one example of the present disclosure may include a differential gear casing defining first and second output shaft openings that are coaxially aligned along the axis of rotation of the differential gear casing. The first and second side gears may be rotatably mounted in the differential gear casing. The first and second side gears may be coaxially aligned along the rotational axis of the differential gear casing. The first side gear may define a first shaft opening configured to provide a first torque transfer connection with the first output shaft received within the first output shaft opening. The second side gear may define a second output shaft opening configured to provide a second torque transfer connection with a second output shaft received within the second output shaft opening. A pair of pinion gears may be mounted between the first side gear and the second side gear. The pinion gear can be rotatably mounted on a cross shaft fixed to rotate with the differential gear casing. The clutch pack may include a plurality of annular plates sandwiched between a plurality of annular friction discs. The clutch pack may be provided on the first side of the cross shaft. The actuator assembly may include a piston received within the piston housing. The actuator assembly may be configured to actuate the clutch pack. The actuator assembly may be provided on a second side opposite the first side of the cross shaft.

According to further features, the differential gear mechanism may further include a plurality of transfer rods connecting the clutch pack and the actuator assembly. The clutch pack may further include a first delivery plate. The actuator assembly may further include a second delivery plate. A plurality of transfer rods can be connected between the first transfer plate and the second transfer plate.

According to other features, the actuator assembly further comprises a retainer, a first needle roller disposed on one side of the piston housing, and a second needle roller disposed on an opposite side of the piston housing . The piston may further include at least one O-ring mounted thereon. The at least one O-ring may be configured to slidably traverse along the piston housing. The actuator assembly may further include a hydraulic fitting extending from an outer diameter of the piston housing. The hydraulic connection port may be configured to communicate the hydraulic fluid from the hydraulic fluid source to the actuator assembly.

In other features, a pair of pinion gears can intermesh with the first and second side gears to form a torque transfer device that generates torque between the pinion gear and the first and second side gears And rotate the first and second side gears about the rotation axis. The torque transmission device may also be configured to cause the first and second side gears to rotate at different rotational speeds with respect to each other about the rotational axis. The clutch pack may be concentric with the first side gear. The actuator assembly may be co-axial with the second side gear.

According to other features, the clutch pack and actuator assembly may be configured at both ends of the differential gear casing. The piston may include a piston body defined around the piston center axis. The piston body may include a central piston wall, an outer diameter piston wall, and an inner diameter piston wall. The piston housing may include a central annular housing wall, an outer annular housing wall and an inner annular housing wall that together define an annular pocket for receiving the piston.

In other features, the differential gear assembly may include a lug formed in one of the piston and the piston housing. The groove may be defined by a groove wall in the other of the piston and the piston housing. The lug can be received in the groove. The engagement of the lug and the groove wall prevents rotation of the piston about the piston central axis. The lug may be formed in the piston. The grooves may be formed in the piston housing. In one configuration, a lug may be formed in the inner diameter piston wall. The grooves may be formed in the inner annular housing wall. The lug may include a pair of lugs configured on the inner piston wall. The grooves may include a pair of grooves formed in the inner annular housing wall. A pair of lugs may be provided in the inner diameter piston wall in diametrically opposed relationship. The pair of grooves may be provided in the inner annular housing wall in diametrically opposite relationship. The outer diameter piston wall may define a first annular groove and the inner piston wall may define a second annular groove. The first O-ring can be received in the first annular groove. The second O-ring can be received in the second annular groove. The first O-ring may be configured to slide transversely along the outer annular housing wall. The second O-ring may be configured to slide transversely along the inner annular housing wall.

The differential gear assembly constructed in accordance with the additional features of the present disclosure may include a differential gear casing defining first and second output shaft openings. The first and second output shaft openings may be coaxially aligned along the rotational axis of the differential gear casing. The first and second side gears may be rotatably mounted in the differential gear casing. The piston may have a piston body defined around the piston center axis. The piston body may include a central piston wall, an outer diameter piston wall, and an inner diameter piston wall. The piston body may be configured to apply an axial force to the clutch pack.

The piston housing may include a central annular housing wall, an outer annular housing wall, and an inner annular housing wall that together define an annular pocket for receiving the piston. The lug may be formed in one of the piston and the piston housing. The groove may be defined by a groove wall in the other of the piston and the piston housing. The lug can be received in the groove. The engagement of the lug and the groove wall can prevent the piston from rotating about the piston central axis. The differential gear assembly may further include a clutch pack. The clutch pack may include a plurality of annular plates sandwiched between a plurality of annular friction discs. The clutch pack may be provided on the opposite side of the differential gear casing from the piston.

The differential gear assembly constructed in accordance with the additional features may include a differential gear casing defining first and second output shaft openings that are coaxially aligned along the axis of rotation of the differential gear casing. The first and second side gears may be rotatably mounted in the differential gear casing. A pair of pinion gears may be mounted between the first side gear and the second side gear. Both pinion gears can be rotatably mounted on a cross shaft fixed to rotate with the differential gear casing. The clutch pack may include a plurality of annular plates sandwiched between a plurality of annular friction discs, and a first transmission plate. The clutch pack may be provided on the first side of the cross shaft. The actuator assembly may include a piston received within the piston housing, and a second transmission plate. The actuator assembly may be configured to actuate the clutch pack. The actuator assembly may be provided on a second side opposite the first side of the cross shaft. A plurality of transfer rods can be connected between the first transfer plate and the second transfer plate.

According to other features, the differential gear assembly may further include a lug formed in one of the piston and the piston housing. The groove may be defined by a groove wall in the other of the piston and the piston housing. The lug can be received in the groove. The engagement of the lug and the groove wall can prevent the piston from rotating about the piston central axis.

The present disclosure will be more fully understood from the following detailed description and the accompanying drawings.

1 is a front perspective view of a differential gear mechanism constructed in accordance with an example of the present disclosure;
Fig. 2 is a sectional view of the differential gear mechanism of Fig. 1 taken along line 2-2,
3 is a cross-sectional view of the differential gear mechanism of FIG. 1 taken along line 3-3,
Figure 4 is a detailed view of the actuator assembly of Figure 1,
Figure 5 is an exploded view of the actuator assembly of Figure 4,
Figure 6 is a perspective view of the piston assembly of the differential gear mechanism of Figure 1,
7 is a cross-sectional view of the piston assembly of FIG. 6 taken along line 7-7, showing a case where the piston is in a relaxed state,
Fig. 8 is a cross-sectional view of the piston assembly of Fig. 7, showing the piston in its fully actuated state; Fig.

Referring first to FIG. 1, there is shown an electronic differential limiting assembly constructed in accordance with the present disclosure, identified generally by reference numeral 10. The electronic differential limiting assembly 10 may generally include a differential gear assembly or mechanism 20, and a clutch assembly 30, which are provided in the differential gear case 22. As shown in FIG. The differential limiting assembly 10 is operable to drive a pair of axle shafts (not shown), which can be received in a housing (not shown) and connected to a drive wheel (not shown). Generally, the differential limiting assembly 10 functions as a conventional open differential during normal operating conditions until a situation where a bias torque is desired occurs. When a loss of traction is detected or predicted, the clutch assembly 30 may be selectively activated to produce an optimal bias ratio for the situation.

2 and 3, the differential gear assembly 20 includes a pair of side gears 40, 42 mounted to rotate with an axle shaft (and first and second drive wheels) . The side gears 40 and 42 define the first and second axle shaft openings 44 and 46 (see FIG. 3). The cross pin or pinion gear shaft 50 may be fixedly mounted to the differential gear case 22 so as to rotate together with the differential gear case 22. The corresponding pair of pinion gears 52 are mounted to rotate together with the pinion gear shaft 50 and engage with the both side gears 40 and 42. As will be described in greater detail below, in the open state, the differential gear assembly 20 serves to rotate the axle shaft at different speeds.

The clutch assembly 30 connects the input of the electronic differential limiting device 10 to the differential gear assembly 20. In some examples, the input portion may include a ring gear fixedly provided around a differential gear case 22 driven by a pinion gear. Clutch assembly 30 may generally include a clutch pack 60 and a clutch actuator assembly 62.

The clutch pack 60 includes a plurality of annular plates 64 sandwiched between a plurality of annular friction discs 68. A plurality of annular plates (64) can be connected to rotate with one of the differential gear case (22) and the differential gear assembly (20). A plurality of annular friction discs 68 may be connected to rotate with the other of the differential gear case 22 and the differential gear assembly 20. A plurality of annular plates 64 are rotatably coupled to the differential gear case 22 (e.g., splined to the inner diameter of the differential gear case 22), a plurality of annular friction discs 68, (E.g., splined to the outer diameter of the side gear 40) with the differential gear assembly 20. It will be appreciated that the annular friction disk 68 may be supported to rotate by either or both of the side gear 40 and the side gear 42. The first transmitting plate 69 may be provided as a part of the clutch pack 60.

A plurality of annular plates 64 and annular friction discs 68 are sandwiched between each other and act to rotate past each other in a substantially non-contact relationship when the clutch assembly 30 is in the open position. However, those skilled in the art will appreciate that the term " non-contacting ", as used herein, is relative, meaning that the annular plate 64 and the annular friction disk 68, when the clutch assembly 30 is in the open state, Will not necessarily be expressly meant to deny that they do not. The annular plate 64 and the annular friction disc 68 are axially movable to frictionally engage with each other so that when the clutch assembly 30 is in the closed or partially closed condition, Thereby reducing the relative rotation between the disks 68. In this way, when the clutch assembly 30 is in the closed position, not only the side gears 40 and 42, but also the axle shaft and the drive wheel rotate together.

The clutch assembly 30 can operate in an open state in which the side gears 40, 42 can rotate independently of each other, e.g., at different speeds. The clutch assembly 30 may also operate in a closed or partially closed state in which the side gears 40, 42 are rotated together or partially together (i.e., not independently), e.g., at substantially the same speed. Clutch assembly 30 includes a hydraulic clutch assembly that utilizes a pressurized hydraulic fluid that may act on actuator assembly 62 to selectively actuate clutch pack 60 between an open, 30).

Referring now specifically to Figures 2-4, actuator assembly 62 will be further described. The actuator assembly 62 is provided at the opposite end of the differential gear case 22 to the clutch pack 60. In one example, the clutch pack 60 may be generally eccentric to the first side gear 40, and the actuator assembly may be generally eccentric to the second side gear. Many advantages are realized as a result of positioning the actuator assembly 62 at the opposite end of the differential gear case 22 to the clutch pack 60. For example, the final package size of the electronic differential limiting device 10 is reduced. The cross shaft 50 is centered between the bearing races. A stock axle shaft having a standard length may be used. The clutch pack 60 may be made larger to provide greater torque capacity. The electronic differential limiting device 10 may be replaced by an "open" differential gear on the same assembly line. Actuator assembly 62 generally includes a retainer 70, a first needle roller 72, a bearing race 74, a piston housing 80, a piston 82, a pair of O-rings 84, And a piston assembly 68 having a roller 88 and a second transfer plate 90. The second transfer plate 90 can act as a bearing race for the second needle roller 88. The piston housing 80 can be mounted in a ring 91 that is seated in the retainer 70.

A plurality of transfer rods 92 are disposed between the second transfer plate 90 of the actuator assembly 62 and the first transfer plate 69 of the clutch pack 60. In the illustrated example, eight transfer rods 92 are disposed between the second transfer plate 90 and the first transfer plate 69. The transmission rod 92 may be evenly spaced around the differential gear casing 22.

Additional features of the piston assembly 68 will now be described with additional reference to Figures 5-8. In operation, the movement of the piston 82 in the left direction (as viewed in FIGS. 2 to 4) causes the transfer rod 92 to compress the first transfer plate 69 in the left direction, Lt; / RTI > Similarly, when the pressure is released from the piston 82, the transfer rod 92 is moved axially to the right (as viewed in FIGS. 2-4) to open the clutch pack 60. The hydraulic fluid may communicate from the hydraulic fluid source (not shown) through the port 98 to the actuator assembly 62.

The piston 82 may include a piston body 100 defined around the piston center axis 102. The piston body 100 may include a central piston wall 110, an outer diameter piston wall 112, and an inner piston wall 114. The outer diameter piston wall 112 may define the first annular groove 120. The inner diameter piston wall 114 may define a second annular groove 122. The first O-ring 84 may be received in the first annular groove 120. The second O-ring 130 can be received in the second annular groove 122. The first and second O-rings 84, 130 may be configured to slide transversely along the piston housing 80.

The piston 82 may define a pair of lugs 140 extending from the inner piston wall 114. The lugs 140 are provided in the piston body 100 in diametrically opposite relationship. As will be appreciated from the discussion below, although the lug 140 is shown as a pair of lugs around the inner piston wall 114, other numbers and other locations of the lug 140 are contemplated.

The piston housing 80 will now be described further. The piston housing 80 may generally include a central annular housing wall 150, an outer annular housing wall 152, and an inner annular housing wall 154. The central annular housing wall 150, the outer annular housing wall 152 and the inner annular housing wall 154 may define annular pockets 156 that receive the pistons 82 together. The piston 82 is configured to be supported and moved within the annular pocket 156 when hydraulic fluid is introduced between the piston 82 and the piston housing 80. The O-rings 84, 130 are sealingly engaged with the piston housing 80. In operation, the piston housing 80 does not rotate.

The piston housing 80 may include a pair of groove walls 160 that define a pair of corresponding grooves 162. In the illustrated example, the grooves 162 are formed in the inner annular housing wall 154 in diametrically opposite relationship. The groove 162 is provided in the form of a reduced thickness portion formed in the inner annular housing wall 154.

As will be appreciated from the discussion below, the grooves 162 are shown as a pair of grooves around the inner annular housing wall 154, although other numbers of grooves and other locations are contemplated. Further, although the lug 140 is shown as part of the piston 82 and the groove is shown as part of the piston housing 80, these features may be inverted. Optionally, the piston housing 80 may incorporate one or more lugs with one or more grooves while the piston 82 may incorporate one or more grooves with one or more grooves. The rotation of the piston 82 around the piston central axis 102 is prevented by the relationship between the lug 140 and the groove 162. In this regard, the lug 140 may engage the groove wall 160 to limit the rotation of the piston 82 about the piston center axis 102 (see FIG. 6).

As noted above, the piston assembly 62 may further include a hydraulic port 98 configured on the piston housing 80. The hydraulic port 98 may be configured to communicate hydraulic fluid from the piston assembly 68. In the illustrated example, the hydraulic port 98 is formed in the outer annular housing wall 152. The hydraulic port 98 may extend along the port longitudinal axis 172. The port longitudinal axis 172 may traverse the piston center axis 102 (see FIG. 6). The hydraulic port 98 may communicate hydraulic fluid from a hydraulic fluid source (not shown) to the actuator assembly 62.

In operation, the piston 82 may move from a relaxed state (see FIG. 7) to an exerted state (see FIG. 8). 7 and 8, in both conditions, the lug 140 of the piston 82 is maintained in engagement with the groove 162 of the piston housing 80, so that the piston center axis 102 6) of the piston (82). In some embodiments, the axial force may be large enough to rotate the piston 82 within the piston housing pocket 156. Such a situation is undesirable because it may cause galling, premature wear and / or tearing of the sealing features of the piston assembly 62. The lug and groove features provided by the piston assembly 62 of the present teachings exclude such situations. As another advantage, the piston assembly 68 provides anti-rotation features without an increase in parts. In this regard, additional components such as, but not limited to, dowel pins, clips and fasteners are not required.

The above description of the present embodiment has been provided for illustration and explanation. It is not intended to be exhaustive or to limit the present disclosure. The individual elements or features of a particular embodiment are not generally limited to that specific embodiment, and may be used in alternate and selected embodiments, if appropriate, not specifically shown or described. The individual elements or features of the specific embodiments mentioned may also be varied in many ways. Such modifications are not to be regarded as a departure from the present disclosure, and all such modifications are intended to be included within the scope of this disclosure.

Claims (20)

In the differential gear assembly,
A differential gear casing defining first and second output shaft openings, wherein the first and second output shaft openings are coaxially aligned along an axis of rotation of the differential gear casing;
First and second side gears rotatably mounted within the differential gear casing and coaxially aligned along the axis of rotation of the differential gear casing, the first side gear comprising a first and a second side gear housed within the first output shaft opening, The second side gear defining a first shaft opening configured to provide a first torque transfer connection with the output shaft, the second side gear providing a second torque transfer connection with a second output shaft received within the second output shaft opening The first and second side gears defining a second output shaft opening configured;
A pair of pinion gears mounted between the first side gear and the second side gear, wherein both pinion gears are rotatably mounted on a cross shaft fixed to rotate together with the differential gear casing; A pair of pinion gears;
A clutch pack including a plurality of annular plates sandwiched between a plurality of annular friction discs, the clutch pack being provided on a first side of the cross shaft; And
An actuator assembly including a piston received in a piston housing and configured to actuate the clutch pack, the actuator assembly being provided on a second side opposite the first side of the cross shaft
Differential gear assembly. The method according to claim 1,
Further comprising a plurality of transfer rods connecting the clutch pack and the actuator assembly
Differential gear assembly. 3. The method of claim 2,
Wherein the clutch pack further comprises a first transfer plate, the actuator assembly further comprising a second transfer plate, the plurality of transfer rods being connected between the first transfer plate and the second transfer plate
Differential gear assembly. The method according to claim 1,
The actuator assembly further includes a retainer, a first needle roller disposed on one side of the piston housing, and a second needle roller disposed on an opposite side of the piston housing
Differential gear assembly. 5. The method of claim 4,
Wherein the piston further comprises at least one O-ring mounted to the piston, the at least one O-ring being configured to slidably traverse along the piston housing
Differential gear assembly. The method according to claim 1,
The actuator assembly further includes a hydraulic fitting extending from an outer diameter of the piston housing and the hydraulic connection port configured to communicate hydraulic fluid from a hydraulic fluid source to the actuator assembly
Differential gear assembly. The method according to claim 1,
Wherein the pair of pinion gears are meshed with the first and second side gears to form a torque transmitting device, and the torque transmitting device transmits torque between the pinion gear and the first and second side gears, 1 and second side gears about a rotational axis, and the torque transfer device is also configured to rotate the first and second side gears at different rotational speeds relative to each other about an axis of rotation
Differential gear assembly. The method according to claim 1,
Wherein the clutch pack is generally concentric with the first side gear and the actuator assembly is generally coaxial with the second side gear
Differential gear assembly. The method according to claim 1,
Wherein the clutch pack and the actuator assembly are configured at both ends of the differential gear casing
Differential gear assembly. The method according to claim 1,
Wherein the piston includes a piston body defined about a piston center axis, the piston body including a central piston wall, an outer diameter piston wall and an inner diameter piston wall, the piston housing having an annular pocket for receiving the piston A central annular housing wall defining an outer annular housing wall and an inner annular housing wall,
Differential gear assembly. The method according to claim 1,
A lug formed in one of the piston and the piston housing; And
Further comprising a groove defined by a groove wall on the other of the piston and the piston housing,
The lug is received in the groove and the engagement of the lug and the groove wall prevents rotation of the piston about the piston center axis
Differential gear assembly. 12. The method of claim 11,
Said lug being formed in said piston, said groove being formed in said piston housing
Differential gear assembly. 13. The method of claim 12,
Said lug being formed in said inner piston wall, said groove being formed in said inner annular housing wall
Differential gear assembly. 14. The method of claim 13,
Said lug comprising a pair of lugs configured in said inner piston wall, said groove comprising a pair of grooves formed in said inner annular housing wall
Differential gear assembly. 15. The method of claim 14,
Said pair of lugs being provided in said inner diameter piston wall in diametrically opposite relationship and said pair of grooves being provided in said inner annular housing wall in diametrically opposite relationship
Differential gear assembly. 15. The method of claim 14,
Wherein the outer diameter piston wall defines a first annular groove, the inner diameter piston wall defines a second annular groove, a first O-ring is received in the first annular groove, and a second O- Wherein the first O-ring is configured to slide transversely along the outer annular housing wall and the second O-ring is configured to slide transversely along the inner annular housing wall
Differential gear assembly. In the differential gear assembly,
A differential gear casing defining first and second output shaft openings, wherein the first and second output shaft openings are coaxially aligned along an axis of rotation of the differential gear casing;
First and second side gears rotatably mounted in the differential gear casing;
CLAIMS What is claimed is: 1. A piston comprising a piston body defined about a piston center axis, said piston body comprising a central piston wall, an outer diameter piston wall and an inner piston wall, said piston body configured to exert an axial force on the clutch pack, piston;
A piston housing having a central annular housing wall defining an annular pocket for receiving the piston, an outer annular housing wall and an inner annular housing wall;
A lug formed in one of the piston and the piston housing; And
And a groove defined by a groove wall in the other of the piston and the piston housing,
The lug is received in the groove and the engagement of the lug and the groove wall prevents rotation of the piston about the piston center axis
Differential gear assembly. 18. The method of claim 17,
The differential gear assembly further comprising the clutch pack,
Wherein the clutch pack includes a plurality of annular plates sandwiched between a plurality of annular friction discs, wherein the clutch pack is mounted on a side of the differential gear casing opposite to the piston
Differential gear assembly. In the differential gear assembly,
A differential gear casing defining first and second output shaft openings, wherein the first and second output shaft openings are coaxially aligned along an axis of rotation of the differential gear casing;
First and second side gears rotatably mounted in the differential gear casing;
And a pair of pinion gears mounted between the first side gear and the second side gear, wherein both pinion gears are rotatably mounted on a cross shaft fixed to rotate together with the differential gear casing, Gear;
A first transmitting plate, and a plurality of annular plates sandwiched between a plurality of annular friction discs, the clutch pack being provided on a first side of the cross shaft;
An actuator assembly including a second transmission plate and a piston received within the piston housing, the actuator assembly being configured to actuate the clutch pack, the actuator assembly being provided on a second side opposite the first side of the cross shaft; And
And a plurality of transfer rods connected between the first transfer plate and the second transfer plate
Differential gear assembly. 20. The method of claim 19,
A lug formed in one of the piston and the piston housing; And
Further comprising a groove defined by a groove wall on the other of the piston and the piston housing,
The lug is received in the groove and the engagement of the lug and the groove wall prevents rotation of the piston about the piston center axis
Differential gear assembly.

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